Field of the Invention
The present invention relates to an apparatus for measuring saturated hydraulic conductivity of unsaturated porous media in the field.
Description of the Related Art
Field measurements on the saturated hydraulic conductivity of porous media in an unsaturated zone are typically performed using a standpipe permeameter test, a method using aseepage meter and the hydraulic gradient between surface water and subterranean water, a slug test based on an instantaneous change in the water level, and an estimation method using an empirical formula based on particle size analysis of field-sampled porous media in a laboratory on field-sampled porous media. However, these methods have rather low objective reliability. For example, it is difficult to apply the standpipe permeameter and the method using a seepage meter and the hydraulic gradient between surface water and subterranean water in a place in which the interaction between surface water and subterranean water is active. Using the slug test to measure hydraulic conductivity, which is the lateral hydraulic conductivity of porous media to be measured, also requires vertical hydraulic conductivity to be measured therefrom. The estimation method using an empirical formula based on particle size analysis is accompanied with the sampling of porous media and post-test treatment, which consequently lowers the reliability of the test. A field saturated hydraulic conductivity measuring device recently developed and published (Korean Patent No. 10-1366057) shows a highly-reliable field assessment result. However, this device is designed to measure the hydraulic conductivity of surface water and the hydraulic conductivity of a lower portion of porous media.
A variety of methods are used for measuring the hydraulic conductivity of porous media in an unsaturated zone. Among these methods, a tension disk infiltration system, a Guelph infiltration system, a double-ring infiltration system, a velocity permeameter, and the like are generally used. However, each of these systems is also estimated as having low objective reliability in a field measurement of saturated hydraulic conductivity.
In the meantime, in order to measure the hydraulic conductivity using Darcy's Law, Darcian flux and a hydraulic gradient of a range to be measured is required. The hydraulic gradient can be obtained by measuring the amount of water supplied to a cylinder and a head difference of the range to be measured. The amount of water supplied to the cylinder in a steady state can be obtained using a metering pump, such as a peristaltic pump, or a Marriott's bottle (refer to Korean Patent No. 10-1252136). In order to visually measure the head difference in the range to be measured, the hydraulic head at the depth to be measured must be formed above the earth surface. When water having a certain pressure head is supplied along the earth surface within the cylinder, a head loss proportionally increases with increases in the depth of the portion of porous media to be measured. When the range to be measured is positioned deep, the hydraulic head at the corresponding depth is proportionally lowered. So, it is difficult to measure the hydraulic head from the earth surface. In order to overcome this, a method of minimizing the head loss of the pressure head by directly supplying water to the portion directly above the range to be measured without causing the water to flow through porous media at the corresponding depth is required.
The information disclosed in the Background of the Invention section is only for the enhancement of understanding of the background of the invention, and should not be taken as an acknowledgment or as any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.